Soft formation core barrel

ABSTRACT

A core barrel device for producing and retrieving subterranean cores, particularly from soft or unconsolidated formations, utilizes a fluid-pressure collapsible sleeve above the corer to receive and hold the core material and permit its retrieval in its original subterranean condition. Pressure responsive valves maintain a fluid pressure behind the collapsible sleeve to retain it in the collapsed position until the core is received in the sleeve and also permit fluid behind the sleeve to exhaust as the core enters the sleeve while the sleeve continues to offer lateral pressure support for the core and also remains collapsed above the core. When the coring device is withdrawn, a small amount of core material falls from the lower portion of the core barrel and the lower portion of the sleeve collapses to retain the remainder of the core within the core barrel.

nite States Patent [72] Inventor Maurice P. Lebourg 3,383,131 /1968 Rosfelder 175/243 X 3700 Greenway Plaza Drive Suite 428, 3,480,093 1 H1969 Clynch 175/58 Houston, Tex. 77027 3,51 1,324 5/1970 Pieters et al. 175/245 X [21] Appl. No. 22,251 3,525,409 8/1970 Holzman 175/245 2: t d r Primary ExaminerStephen J. Novosad 1 a en e o Attorneys-Arnold, White & Durkee, Tom Arnold, Bill Durkee, Jack C. Goldstein, John F. Lynch, Louis T. Pirkey, Frank Vaden, and Robert 27 Claims, 6 Drawing Figs. [52] [1.5. CI 175/58, ABSTRACT: A core barrel device for producing and retrievl75/243, 175/245, l75/20 ing subterranean cores, particularly from soft or uncon- [51] int. Cl E2lb 9/20, solidated formations, utilizes a fluid-pressure collapsible 13211) /00 sleeve above the corer to receive and hold the core material Field of Search 175/58, 20, and permit its retrieval in its original subterranean condition. 243, 245, 250, 49, 77, 78, 308, 403, 405, 233, 239 Pressure responsive valves maintain a fluid pressure behind the collapsible sleeve to retain it in the collapsed position until [56] References Cited the core is received in the sleeve and also permit fluid behind UNITED STATES PATENTS the sleeve to exhaust as the core enters the sleeve while the 1,853,531 4/1932 schmissrauter et a] 0 1755 X sleeve continues to offer lateral pressure support for the core 2,393,691 7/|959 Johnson 175,250 X and also remains collapsed above the core. When the coring 2 9 7 77 3/1960 Hildebrand |/245X device is withdrawn, a small amount of core material falls 2,927,776 3/1960 Hildebrandtetal. 245 x from the lower Portion of the core barrel and the lower P 3 349 57 0 9 7 Hildebrand [75/250 tion of the sleeve collapses to retain the remainderof the core within the core barrel.

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SHEET 2 OF 3 Maurice P. Lebourg INVENTOR Awmwmwwm ATTORNEYS PATENTEDNnv 23 I97! SHEET 3 OF 3 Maurice P. Lebou IN VE N TOR ATTORNEYS SOFT FORMATION CORE BARREL BACKGROUND OF THE INVENTION The instant invention relates to a method and apparatus for producing and retrieving subterranean cores. More particularly, the instant invention relates to the method and apparatus for obtaining subterranean cores from soft or unconsolidated formations in a condition which is properly representative of the strata in the formation.

It has heretofore been found difficult to secure proper cores from certain types of soft or unconsolidated formations in well bores. Soft or unconsolidated formations or conglomerates of badly fractured rock often tend to be washed away by the fluid circulating to the coring bit or otherwise crumble or disintegrate upon retrieval or handling so that the cores from these formations are not truly representative of the subterranean strata being investigated.

It can be readily appreciated that when coring such soft or unconsolidated formations, special apparatus is necessary to maintain the integrity of the core and to prevent the core from disintegrating or falling out of the core barrel when it is attempted to retrieve the core.

Soft formation core barrels have been developed in the prior art for the purpose of maintaining the integrity of an unconsolidated formation core. In one aspect, these core barrels have involved apparatus wherein an elastic sleeve is adapted to move upwardly into a tubular member and encase the core as the core enters the tubular member. Such apparatuses impress a columnar load on the core inasmuch as the upward force of the core is required to move the sleeve. Moreover, these devices suffer disadvantages since there is no effective way to close the elastic sleeve and prevent the core material from disintegrating and falling from the core barrel during retrieval of the core and since the moving parts of a core barrel of this nature can become jammed and inoperative during use.

Typical folded sleeve apparatuses of this kind are disclosed in U.S. Pat. Nos. 3,092,191 and 2,927,776. I

Another prior art device shown in U.S. Pat. No. 2,893,691 for accommodating nonconsolidated cores involves the use of a collapsible sleeve of inelastic material which could be collapsed below the core when the coring operation was complete. Other attempts to retrieve nonconsolidated cores have involved simply closing an elastic sleeve with an independent source of pressure to capture the core after the coring operation is complete, such as in U.S. Pat. No. 3,480,093.

SUMMARY OF THE INVENTION It is accordingly an object of the instant invention to provide a method and apparatus for producing and retrieving subterranean formation cores while maintaining said cores in their natural undisturbed condition.

It is a further object of this invention to provide a method and apparatus for producing and retrieving soft formation cores which utilizes fluid pressure to laterally support the core during its formation and retrieval.

It is among the further objects of this invention to provide a core barrel apparatus wherein effective closure below the core is accomplished to enable retrieval of the core without crumbling or loss of core material.

It is among the other objects of this invention to provide a method and apparatus for producing and retrieving soft formation cores which is adaptable to rotary coring procedures as well as other coring procedures which do not involve rotary drilling.

It is included in the further objects of this invention to provide a soft formation core barrel apparatus wherein the core is accepted into the apparatus with minimum imposition of forces on the core itself.

It is among the further objects of this invention to provide a method and apparatus for producing and retrieving soft formation cores which utilizes a fluid-pressure collapsible member to hold the core during production and retrieval.

The above and other objects are accomplished by the method of the instant invention which comprises cutting a subterranean core formation to produce a core, accepting the core axially into a collapsible sleeve, supplying a fluid pressure on the outer surface of the sleeve to collapse the sleeve above the core, and controlling the fluid pressure behind the sleeve to permit yieldable expansion of the sleeve from the collapsed position to an expanded position to accept the core.

This method is accomplished by a novel and unique apparatus for producing and retrieving subterranean cores, particularly cores of unconsolidated formations which apparatus comprises a means for cutting the formation to produce a core, a collapsible sleeve means disposed above the cutting means for internally receiving the core produced, and means for producing the fluid pressure on the outer surface of the sleeve, which fluid pressure is greater than the fluid pressure within the sleeve to maintain the sleeve in a collapsed position until the core is received within the sleeve. Pressure valves are provided to maintain the sleeve in collapsed position above the core but to exhaust fluid behind the sleeve as the core enters the sleeve and expands it.

In particular, the novel apparatus of this invention utilizes a coring device wherein fluid flow in the vicinity of the cutting means is utilized to assist in eroding the formation and forming the core and wherein the pressure drop resulting from the restriction flow of such fluid to the cutting region across the tool itself is utilized to provide the pressure differential for collapsing a sleeve and moving an intact column of core material into the tube so that it might be later extracted for examination. Thus, the fluid pressure on the sleeve of the coring apparatus of this invention may be maintained throughout the coring operation, in most circumstances without providing an independent pressure line with a source of pressure to the tool.

Control of fluid pressure behind the collapsible sleeve accomplished by appropriate valves assures that the fluid pressure behind the sleeve is greater than the fluid pressure within the sleeve by a preselected amount so that the sleeve serves to yieldably accept the coring operation to capture the core without crumbling or disintegration.

Although in the oil drilling arts the term fluid is often taken to mean liquid, it is expressly pointed out that the term fluid pressure" as used herein with reference to a pressure on the collapsible sleeve of the coring apparatus of this invention includes pressure which may be supplied by a liquid or a gaseous fluid. In accordance with one specific embodiment of this invention, particularly those apparatuses for coring by the rotary method, it will be seen that a usually liquid drilling fluid is used to exert the fluid pressure to collapse the sleeve. The instant invention is also clearly applicable to gas drilling, e.g., air drilling, by the rotary method in which case the gaseous fluid will collapse the sleeve.

It will be apparent upon consideration of the embodiments shown in this invention that the novel apparatus and method of the instant invention may be adapted to producing and retrieval of cores during rotary drilling, as well as the production and retrieval of subterranean cores using coring techniques which do not involve rotary drilling.

DETAILED DESCRIPTION OF THE DRAWINGS The instant invention will be more particularly understood by reference to the specific embodiments illustrated in the accompanying drawings. FIG. 1A is a partial, sectional view of the upper portion of a specific embodiment of a core barrel apparatus in accordance with this invention which may be used in rotary coring techniques.

FIG. 1B is a partially sectional view of the bottom portion of the same embodiment of coring apparatus shown in F 16. 1A.

FIG. 2 is a sectional view of the coring apparatus of the instant invention showing the position of the collapsible sleeve during the core retrieval of the operation.

FIG. 3 is a sectional view along line 3-3 of FIG. 2 showing the configuration of the collapsible sleeve in its collapsed state.

FIG. 4 is a cross-sectional view of an alternate embodiment of a sleeve which may be used in accordance with the coring apparatus of the instant invention.

FIG. 5 is an illustration of another embodiment of a coring apparatus for use in nonrotary coring techniques and suitable for use in obtaining cores from the subsurface under a body of water.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS The coring apparatus illustrated in FIGS. IA, 18, and FIG. 2 is the type of apparatus adapted to be lowered into a well bore being drilled by the rotary drilling method. In general, the coring apparatus shown in FIGS. 1A, 1B, and in FIG. 2 has an upper mandrel which rotates with the drill string and from which extends an outer surrounding tube which rotates with the mandrel and the drill string. A coring bit is mounted on the lower end of this outer tube. An inner mandrel is suspended from the outer mandrel by bearings so that it does not rotate with the drill string. In this inner mandrel the core supporting apparatus is provided.

With specific reference to FIGS. 1A and 1B, the coring apparatus 100 is adapted to be lowered to the bottom A of a well bore B by means of a string of pipe, the lowermost section of which is illustrated as 11. The lower end of pipe section is threadedly attached to the upper end of outer mandrel 13 of the coring apparatus. Lower pipe section 11 and upper mandrel member 13 together define central channel 15 through which drilling fluid, such as drilling mud, may be circulated down the drill string to the coring bit. Fluid passage 17 in the lower portion of mandrel 13 directs the fluid through the coring apparatus as will be explained below.

Outer tube 21 threadedly engages outer mandrel l3 and extends downwardly therefrom to surround the lower portion of the coring apparatus. The outer tube 21 may desirably be comprised of a number of tubular engaging sections, such as sections 23, 25, and 27 in order that the length of the coring apparatus can be varied in accordance with the depth of the core desired.

The lower portion of outer mandrel 13 is threaded with an inner tubular sleeve 29 which together with bore 38 in the lower end of mandrel 13, forms a cylindrical recess which accommodates the upper end 40 ofinner mandrel 39. The inner surface of tubular sleeve 29 is provided with bearing surfaces 31 which define a race for bearings such as 33 and 34. These bearings serve to suspend inner mandrel 39 from outer mandrel 13. Additional bearing surfaces 41 on the outer surface of inner mandrel 39 complete the race for the bearings and together with the bearings support inner mandrel 39 to freely rotate with respect to outer mandrel 13 and the drill string 11. Other bearing arrangements can be used as will be obvious to those skilled in the art.

Outer tube 19 and inner tubular sleeve 29 together define the upper portion of a fluid channel 20. The channel extends to coring bit 30 and directs the drilling fluid down to the coring bit. Coring bit 30 is illustrated is a diamond coring bit, but it is pointed out that any suitable bit or formation cutting means may be used.

From inner mandrel 39 is suspended the portion of the apparatus in which the core is retained and retrieved. An inner core s'leeve support member 37 terminates in an upper tubular extension 36 which is threaded to inner mandrel 29 at 35. The central opening in tubular extension 36 communicates with bore 44 and fluid passageway 45 in which is positioned oneway check valve 43. Valve 43 is typically of the type involving a ball adapted to move downwardly into a companion seat 42 to block the passage in tubular extension 36 and prevent downward flow of fluid into the inner core barrel. The ball is adapted to move upwardly from its seat to permit fluid within the inner core barrel to exhaust as the core advances in the inner core barrel.

Core barrel member 47 is also threadedly engaged with and suspended from inner mandrel 39. The upper portion of core barrel 47 receives tubular extension 36 of the sleeve support and a fluid seal between the two members is effected with O- ring 51. The lower portion of core barrel 47 is provided with a core catcher 69 such as is known in the art and is positioned above coring bit 30. In the event the lower portion portion of the formation being cored is sufficiently consolidated to be gripped and held by a core catcher, the coring device with catcher will aid in retrieval of the core intact.

Core sleeve 53 is flexible elongated member adapted to receive and grip the unconsolidated core 60 as it enters the core barrel. The upper portion of sleeve 53 is secured in a fluidtight manner to sleeve support member 37 and 55. The lower portion of the sleeve is likewise secured in a fluidtight manner of the sleeve is likewise secured in a fluidtight manner to the lower portion of core barrel member 47 by means of crimping ring 58 and with aid ofO-ring 56.

It will be noted that behind sleeve 53 and between the sleeve and core barrel member 47 there is defined an annular volume 67. The annular volume between the sleeve and core barrel 47 communicates through annular passageway 65 between the core sleeve support member 37 and core barrel 47 with chamber 71. Mounted in the upper portion of core barrel 47 and communicating between chamber 71 and fluid channel 20 are two one-way pressure responsive valves 49 and 79. Valve 49 is a one-way valve permitting flow from channel 20 to volume 71 in response to a pressure gradient across the valve. Similarly, valve 79 is a one-way check valve permitting flow from chamber 71 to channel 20 in response to a pressure gradient in the opposite direction.

Consequently, in response to a positive pressure gradient of sufiicient magnitude between fluid channel 20 and chamber 71, valve 49 will open and permit flow ofdrilling fluid through passageway 50 and through valve 49 to chamber 71 until a pressure gradient less than the setting of valve 49 is achieved. Similarly, in response to a negative pressure gradient of sufficient magnitude between chamber 71 and channel 20, valve 79 will open and exhaust fluid from chamber 71 to fluid channel 20.

Valve 49 is preset to open to fill annular volume 67 in response to a pressure gradient which is lower than the pressure gradient at which valve 79 is set to open. The function and operation of these valves as well as the function of the pressure settings therefor will be understood with reference to the following explanation of the operation of the apparatus illustrated.

During the drilling operation, the drilling string 11 is rotated to effect rotation of coring bit 30. During this drilling operation, drilling fluid such as an appropriate water or oil base drilling mud is circulated downwardly through channel 15 and through passageway 17 to annular fluid channel 20. Because of the relative restricted nature of channel 20, there is a considerable pressure loss due to fluid friction as the drilling fluid passes down annular channel 20. Consequently, it will be appreciated that the dynamic fluid pressure (i.e., fluid pressure not including increases due to increase of hydrostatic head) at point P opposite channel 50 leading to valve 49 would be considerably greater than the dynamic pressure at P in annular channel 68 of coring bit 30. This drop is dynamic pressure results from frictional loss in annular channel 20 between these two points.

As the drilling fluid reaches the coring bit 30, it will be noted that it passes into an annular channel 68 and then the main body of fluid exits through the bottom of the coring bit through channel 59 from which it is directed against the formation to aid in the drilling operation. A small series of channels illustrated at 61 communicate between annular channel 68 and the interior of the core, however, and a serve to equalize the fluid pressure between the interior of the core barrel and the fluid exiting from channel 59 and circulating upwardly around the drill bit as illustrated by arrow F. In view of this equalization of pressure, the dynamic fluid pressure within the' core 60 will be equal to essentially P In use a of this tool, prior to drilling a circulation of fluid is commenced and immediately there is pressure buildup at point p, opposite passageway 50 of sufficient magnitude to open valve 49 and permit the flow of fluid into volume 71 and through channel 67 to the volume 67 between core barrel 47 and sleeve 53. Sleeve 53 is so constructed that the unsupported portion between crimping ring 58 and sleeve support 55 collapses in response to the fluid pressure behind the sleeve in volume 67. An illustration of a typical embodiment of sleeve 53 in collapsed condition is illustrated in FIG. 3 which will be more fully discussed hereinafter.

The pressure gradient required to open valve 49 and permit flow into chamber 71 is a very small pressure gradient and is not of the same magnitude as represented by the pressure lose between point P and P Consequently, inasmuch as the fluid pressure within the core barrel 60 prior to the commencement of drilling essentially corresponds to P there is no internal fluid pressure within sleeve 53 to oppose the collapse of the sleeve. Furthermore, it will be appreciated that in as much as opposing pressure forces within and without the sleeve are at the same level of height that any pressure discrepancies which might be thought to arise because of the difference in hydrostatic head between points P and P will ultimately cancel out.

Furthermore, as pointed out above, exhaust valve 79 which communicates with chamber 71 and ultimately with volume 67 is set to open at a higher pressure gradient than the setting of valve 49. For example, valve 49 might be said to open at a positive pressure gradient of 2pounds per square inch between annular channel 20 and chamber 71 whereas valve 79 would be said to exhaust chamber 71 only if a -pound per square inch negative pressure gradient between channel and chamber 71 is achieved. Therefore, the combination of inlet check valve 49 and outlet check valve 79 enables the storage of fluid under pressure at a predetermined level within volume 67 behind sleeve 53.

Ad drilling is commenced, circulation of fluid is continued and as a result of the drilling operation and the erosion of the formation by the jet action of the fluid from channel 59, core 60 is produced and enters the body of the core barrel. As core 60 enters the body of the core barrel, it forces the collapsed sleeve 53 to open and simultaneously because of the pressure exerted by the core to expand the collapsed sleeve and reduce volume 67 as a result of the volume pressure of core 60 on the interior of sleeve 53, exhaust check valve 79 opens and exhausts fluid from behind the sleeve. In FIG. 1B, the core 60 is shown partially within sleeve 53 which is collapsed in region 54 above the entering core by a fluid under pressure in volume 67. Fluid pressure within volume 67 also provides lateral sup port for the core in region 52 where the core has already entered sleeve 53.

The setting of exhaust check valve 79, although it must be slightly greater than the setting of inlet check valve 49 should not be so great as to result in a pressure on core 60 which crushes or deforms the core as the core enters the core barrel and attempts to open the collapsed sleeve.

It will be appreciated by those skilled in the art that various pressure settings might be used for valves 49 and 69, and the disclosure above with respect to the settings thereof is deemed purely illustrative.

With reference now to FIG. 2 of the appended drawings, there is illustrated the unique operation of the novel apparatus of this invention during the retrieval of an unconsolidated core.

After the coring operation is completed, rotation of the drilling string is stopped and the entire drilling string including the coring device is lifted from the bottom of the hole A with continued circulation of fluid down to the coring bit through annular channel 20. Although not illustrated in FIG. 2, the entire borehole is typically full of fluid during this operation.

As the coring apparatus is lifted from the bottom of the hole, the lower portion of the unconsolidated core will typically fall out of the coring apparatus to the bottom of the hole as illustrated at 79. However, if the lifting operation is accomplished slowly and circulation is continued or increased during the lifting operation, a continued pressure gradient will be present across valve 49 tending to admit fluid to volume 67 behind sleeve 53 and to collapse the lower portion of the sleeve in the region where the core material dropped thus sealing off the upper main portion of the core and maintaining it intact.

()nce the sleeve has been substantially fully collapsed as illustrated at 75 sealing off the core circulation can be discontinued and the fluid pressure within volume 67 is suflicient to support the core during retrieval operation.

In actual operation it is preferred that as the coring apparatus reaches the bottom of the hole, circulation is begun to collapse sleeve 53 over substantially its entire length. The drilling is then begun with continued circulation maintaining a higher fluid pressure behind sleeve 53 than within the sleeve.

Therefore, as the coring apparatus is lifted off the bottom of the borehole, circulation of fluid is preferably increased to assure that the full pressure gradient across the sleeve permitted by the settings of inlet valve 49 and exhaust valve 79. This will in turn assure a pinching at the bottom of the sleeve in response to any of the lower portions of the core which falls from the core barrel.

As the coring apparatus is raised, the hydrostatic head above the apparatus will be reduced and fluid will exhaust from volume 67 through outlet valve 79 as the fluid within the sleeve decompresses. The valve combination functions to c0ntinually maintain a fluid pressure within volume 67 greater than the fluid pressure within the core, maintaining the sleeve in its pinched position as shown at 75 in FIG. 2.

With specific reference now to FIG. 3 of the illustrated drawings, there is shown a sleeve 53 in accordance with one embodiment of this invention in collapsed condition. As illustrated in FIG. 3, sleeve 53 is collapsed from two points on the periphery thereof at points 83 and 85. Sleeve 53 is constructed so that it is dimensionally stable in a longitudinal direction and so that entry of the core into the sleeve does not cause a longitudinally stretching of the sleeve. Preferably sleeve 53 is not elastic in nature. It is not necessary or preferred in the instant novel apparatus to utilize an elastic member since the support of the core can be accomplished with a nonstickin g, nonelastic member which demonstrates the desirable qualities of collapsibility. Suitable fiber-reinforced plastic such as fiber-reinforced neoprene can be used for construction of the sleeve member in accordance with this invention. A suitable reinforced cloth such as glass cloth may be used. It may be desirable to coat the inside of sleeve 53 with a low-friction coating, such as of polytetrafluoroethylene to minimize frictional resistance to the entry of the core.

In the preferred embodiment shown in FIG. 3, the sleeve is shown to have two longitudinally extending stabilizing cables 87 and 89 which extend through the sleeves and tend to make the sleeve preferentially collapse in the fashion shown. If in mounting the sleeve between support member 37 and crimping ring 58, the sleeve is pulled taut rendering cables 87 and 89 taut, the sleeve will preferentially collapse as shown in FIG. 3. Alternatively, the sleeve may be arranged so that to assume other configurations such as three-point or four-point configurations with cables running longitudinally at the apex of each extension of the sleeve in its collapsed condition.

With reference to FIG. 4, there is shown an alternate embodiment of a collapsible sleeve in collapsed condition. The sleeve shown in FIG. 4 is constructed as a cylindrical tube out of two elongated panels 91 and 93 of a suitable flexible and collapsible material. The sleeve material is preferably stable in the longitudinal direction. The sleeve in FIG. 4 is constructed by overlapping each of the two panels at the ends thereof and fusing the panels together at that point, for example, by thermal bonding a suitable fiber reinforced plastic. The resultant sleeve has an effective double thickness of material at points 95 and 97, and consequently, if stretched taut as pointed out above, will preferably collapse with the double thicknesses at the apices of the sleeve in its collapsed configuration.

Although the apparatus of FIGS. 1 and 2 has been disclosed for operation utilizing fluid pressure of the drilling fluid to collapse the sleeve, the concepts of this invention can be equally applied using fluid pressure in the form of a gaseous medium to collapse the sleeve member 53. In a gas drilling operation, air or a similar gas can be conducted to the coring bit as is the drilling fluid. If desired, an independent source of compressed fluid could be provided in the tool or a line carrying a compressed fluid, gas or liquid, could be separately run to the tool from the surface. The operation of the tool in the latter fashion in a deep borehole would not be practical. In such a gas operated tool it will be also appreciated that the reference to fluidtight seals, for example at the location of crimping ring 58 and at location 55 on the sleeve support would be required to be gastight as well as liquidtight Similarly, the seal at O-ring 51 would be required to be a gastight seal ifa gaseous pressure medium was used. Consequently, in the instant specification, when reference has been made to the creation of a fluid pressure behind sleeve 53, it is to be understood that such fluid pressure can be generated by a gaseous or liquid medium.

Similarly, it should be pointed out that although a specific coring bit 30 has been illustrated that any cutting means operable to cut the formation and to form and produce the core many be used. Thus, for example, in beach sand coring apparatus a simple lower sharpened cutting edge might desirably be used. In other nonrotary coring apparatuses, various cutting means might be used rather than the diamond coring bit illustrated as the cutting means in FIGS. 1 and 2.

Thus, for example, with specific reference to FIG. 5, there is illustrated a coring apparatus in accordance with this invention for the recovery of a nonconsolidated core from beneath a body of water. In the sampling of ocean floor deposits, formations of an unconsolidated nature are often encountered, thus making it difficult to recover the core in an intact condition for examination. The method of coring a submarine surface varies as to equipment. Some coring apparatuses utilize a simple weight operated core, such as illustrated in FIG. 5. Other more elaborate hydraulic units may be used whereby a core barrel is hydraulically pushed into the submarine surface. Alternatively, a propellant may be used to force the core barrel to penetrate the submarine surface.

In the illustrated embodiment of FIG. 5, a weight 101 has pushed the coring to 103 into the submarine surface formation 108. The coring tube is provided with a collapsible sleeve 107, typically of the configuration as illustrated in FIG. 3, which is anchored at each end to provide a fluidtight seal at 106 and 109. A differential piston 104 is maintained in the weight member 101 and communicates with the annulus 111 between sleeve I07 and the coring tube 103. Differential piston exerts a pressure above the hydrostatic pressure and check valve 102 traps this differential pressure in the annulus. An exhaust check valve is provided to exhaust fluid when the core expands the sleeve and is rated at a pressure above the pressure rating of inlet check valve 102. The coring and capture of the core are effected substantially as above with the pressure hehind sleeve 107 serving to pinch in the bottom portion of the sleeve after the apparatus is first lifted.

When bringing the tool to the surface, valve 105 maintains, without excess, the pressure required to hold the core in the sleeve inasmuch as it will slowly exhaust as the hydrostatic head above the tool is reduced.

Once again in FIG. 5 it may be seen that a small amount of the core has been lost when pulling the tool up from the bottom and the sleeve automatically closes to trap the core sample.

It will be apparent from a review of the above discussion that other apparatuses may be used in accordance with the teachings of the specification to accomplish the novel method of this invention. For example, once again with relation to FIG. 5, the differential pressure provided by differential piston 4 could also be provided directly from the surface by a pressure line. Alternatively, a coring device satisfactory for taking sand cores from beaches or the like could be readily constructed for manipulation by hand wherein the coring tube could be pressed into the beach sand by hand. Further, it has been illustrated that the use of fluid jets at the point of cutting means can be used to assist the penetration of the coring tube as is well known in the art.

A number of apparatuses may accordingly be constructed to perform the method of this invention for producing and retrieving a formation core which method involves cutting the formation to produce the core and accepting the core axially into a collapsible sleeve, supplying a fluid pressure on the outer surface of the sleeve to collapse the sleeve above the core and controlling that fluid pressure behind the sleeve to permit a yieldable expansion of the sleeve from the collapsed position to an expanded position to accept the core. The novel method of this invention further involves in particular reference to carrying out this invention in rotary drilling methods, establishing a loss of dynamic fluid pressure from a point above the bottom of the hole (upstream in the fluid path) to a point proximate the bottom of the hole, equalizing the dynamic fluid pressure at the bottom of the borehole with the dynamic fluid pressure around the core, and utilizing the higher pressure to support and trap the core during retrieval operation. 7

This method is accomplished by establishing a fluid flow path which produces a dynamic fluid pressure loss in the fluid flowing to the coring bit, directing a circulating drilling fluid through this channel, and collapsing the sleeve by means of the pressure differential in the circulating fluid produced by flow through such fluid flow path.

The apparatuses of this invention may be varied in constructional detail as will be apparent to those skilled in the art. For example, in the apparatus illustrated in FIG. 18, wherein one inlet and one exhaust check valve are illustrated, it might be desirable to place a total of four check valves to function as two inlet valves and two exhaust valves. In addition, it will be appreciated that the lower portion of the sleeve in the area anticipated collapse upon retrieval of the core could be advantageously provided with a thinner wall section or with other means which would cause the sleeve preferentially to collapse in that region and support the core during retrieval.

Other variations will be obvious to those skilled in the art.

What is claimed is:

1. Apparatus for producing and retrieving a formation core which comprises:

means for cutting the formation to produce a core;

a collapsible sleeve means disposed above said cutting means for internally receiving the core produced; means for introducing a fluid under pressure on the outer surface of said sleeve greater than the fluid pressure within said sleeve for maintaining said sleeve in a collapsed position until the core is received therein; and

means for exhausting said fluid in contact with the outer surface of said sleeve for permitting expansion of said sleeve as said core enters said sleeve.

2. The apparatus ofclaim 1 including:

a tubular core barrel structure;

means for mounting said cutting means at the lower end of said core barrel; and

means for mounting said sleeve means within said core barrel structure above said cutting means to provide a volume between the outer surface of said sleeve means and said core barrel wherein a fluid may be maintained under pressure.

3. The apparatus of claim 2 including means for introducing a fluid to said volume at a pressure greater than the fluid pressure within said sleeve means.

4. The apparatus of claim 2 including:

means for interconnecting said core barrel structure in a rotary well drilling string.

5. The apparatus ofclaim 2 including fluid channel means in said core barrel structure for directing a drilling fluid to the region of said cutting means.

6. The apparatus of claim 5 including first valve means disposed between said channel means and said volume to admit fluid to said volume at a first fluid pressure level; and

second valve means disposed between said channel means and said volume to exhaust fluid from said volume at a second fluid pressure level wherein said second fluid pressure level is greater than said first fluid pressure level.

7. The apparatus of claim including fluid jet means in said cutting means communicating with said fluid channel means, said jet means being disposed to direct fluid toward the formation around the core to assist in cutting and forming the core.

8. The apparatus of claim I wherein said sleeve means includes at least two longitudinally disposed reinforcing means arranged at spaced positions at the periphery of said sleeve means to permit said sleeve means to collapse from at least said position on its periphery.

9. The apparatus of claim 1 wherein said sleeve has a preferentially collapsible portion near the bottom thereof.

10. An apparatus for producing and retrieving subterranean formation cores which comprises:

a tubular core barrel means;

cutting means disposed at the lower portion of said core barrel means for cutting said core;

collapsible sleeve means disposed within said core barrel means above said cutting means and defining a volume between the outer surface of said sleeve means and said core barrel, wherein fluid may be maintained under pressure;

first valve means to maintain a fluid within said volume at a preselected pressure greater than the fluid pressure within said sleeve to maintain said sleeve in collapsed position until said core is received therein; and

second valve means to exhaust fluid from said volume in response to decrease of said volume resulting from said core entering said sleeve.

11. The apparatus of claim 10 wherein said tubular core barrel means comprises an outer barrel and an inner barrel defining a fluid channel therebetween, and wherein said first and second valve means communicate between said channel and said volume.

12. The apparatus of claim 11 including means for exhausting fluid from said volume to said fluid channel means when said core enters said sleeve.

13. The apparatus of claim 12 wherein said means for admitting fluid and said means for exhausting fluid comprise first and second one-way check valves which open at predetermined pressure gradients, and wherein the pressure gradient required to open said second valve is greater than that required to open said first valve.

14. The apparatus of claim 11 wherein said outer barrel includes means for interconnection in a rotary well drilling string and wherein said outer barrel is rotatable independent of said inner barrel.

15. The apparatus of claim 11 including fluid jet means in said cutting means communicating with said fluid channel means, said fluid jet means being disposed to direct fluid against the formation around the core to assist in the cutting and formation of said core.

16. The apparatus of claim 11 wherein said means for admitting fluid is located at first position in said fluid channel means and including pressure equalizing means located at a second position in said fluid channel means downstream from said first position, said pressure equalizing means communicating between said fluid channel means and the interior of said sleeve to equalize fluid channel means and the interior of said sleeves to equalize fluid pressure therebetween.

17. The apparatus of claim 10 including at least two longitudinal reinforcing means disposed around the periphery of said sleeve at regularly spaced positions and adapted to maintain the outer surface of said sleeve proximate to the inner surface of said inner barrel at said positions and permitting said sleeve means to collapse from said positions on its periphery in response to fluid pressure within said volume.

18. Apparatus for producing and retrieving a formation core by rotary drilling which comprises:

a core barrel structure comprising an outer barrel and an inner barrel defining a fluid channel therebetween, said outer barrel being freely rotatable relative to said inner barrel;

a cutting means mounted on the lower portion of said outer barrel and rotatable with said outer barrel for cutting the fonnation to produce a core, said cutting means providing the termination of said fluid channel means;

a tubular, collapsible sleeve disposed within said inner barrel above said cutting means for internally receiving the core produced, said sleeve means defining a volume between the outer surface thereof and said inner barrel;

first check valve means for admitting fluid from a first position in said channel to said volume at a first pressure greater than the fluid pressure within said sleeve to collapse said sleeve prior to receipt or the core therein;

second check valve means for exhausting fluid from said volume to said channel at a second pressure greater than said first pressure, said second pressure being insufficient to deform said core; and

pressure equalization means disposed to equalize the fluid pressure between a second position in said channel downstream of said first position and the volume within said sleeve.

19. Apparatus for producing and retrieving formation cores from beneath the surface of a body of water which comprises:

a coring tube;

cutting means on the lower end of said tube for producing said core;

a collapsible sleeve disposed within said tube, said sleeve defining a sealable volume capable of retaining a fluid under pressure;

differential pressure means to supply a fluid to said volume at a fluid pressure greater than hydrostatic pressure;

exhaust check valve means disposed to exhaust fluid within said volume to said body of water, said check valve being openable in response to a preselected gradient between said pressure within said volume and hydrostatic pressure.

20. A method for producing and retrieving a formation core which comprises:

cutting the formation to produce a core;

accepting said core axially into a collapsible sleeve;

applying a fluid pressure to the outer surface of said sleeve to collapse said sleeve above said core; and

controlling said fluid pressure behind said sleeve to permit yieldable expansion of said sleeve from the collapsed position to an expanded position to accept said core.

21. The method of claim 20 wherein said core is cut by rotary drilling.

22. The method of claim 20 including the step of circulating a fluid to the formation in the cutting region to assist in cutting said core.

23. The method of claim 20 wherein said core is retrieved from a location under a hydrostatic head of pressure including the steps of raising said core while in said sleeve, and

reducing said fluid pressure behind said sleeve in response to the reduction of hydrostatic pressure as said core is raised.

24. A method for producing and retrieving a formation core from a borehole which comprises:

cutting the formation to produce a core;

establishing a fluid flow path to circulate a fluid to the bottom of said borehole in the cutting region, said fluid flow path offering resistance to said fluid flow to create a dynamic pressure drop across said path from a first position above the bottom of said borehole to a second lower position proximate the bottom of said borehole;

accepting said core axially into a collapsible sleeve;

ll 12 applying a fluid pressure corresponding to said fluid preslifted from the bottom of said borehole;

sure at said first position to the outer surface of said permitting the lower portion of said core to fall to the botsleeve to collapse said sleeve above said core; tom of said borehole; and equalizing dynamic fluid pressure between fluid at said collapsing said sleeve below the remainder of said core to second position and fluid within said sleeve; and p re id orecontrolling said pressure behind said sleeve to permit 7. The method of claim 24 wherein said borehole is filled yieldable expansion of said sleeve to accept said core. Wilh li (luid i ncludin g additional pof 25. The method of claim 24 wherein said core is cut by roralsmg 531d core said borehole; and wry drilling reducing the pressure behind said sleeve in response to the The method f l i 2 induding the Steps f IO reduction of hydrostatic pressure as said core is raised in lifting said core from the bottom ofsaid borehole; Smd boreholecontinuing circulation in said fluid path while said core is 

2. The apparatus of claim 1 including: a tubular core barrel structure; means for mounting said cutting means at the lower end of said core barrel; and means for mounting said sleeve means within said core barrel structure above said cutting means to provide a volume between the outer surface of said sleeve means and said core barrel wherein a fluid may be maintained under pressure.
 3. The apparatus of claim 2 including means for introducing a fluid to said volume at a pressure greater than the fluid pressure within said sleeve means.
 4. The apparatus of claim 2 including: means for interconnecting said core barrel structure in a rotary well drilling string.
 5. The apparatus of claim 2 including fluid channel means in said core barrel structure for directing a drilling fluid to the region of said cutting means.
 6. The apparatus of claim 5 including first valve means disposed between said channel means and said volume to admit fluid to said volume at a first fluid pressure level; and second valve means disposed between said channel means and said volume to exhaust fluid from said volume at a second fluid pressure level wherein said second fluid pressure level is greater than said first fluid pressure level.
 7. The apparatus of claim 5 including fluid jet means in said cutting means communicating with said fluid channel means, said jet means being disposed to direct fluid toward the formation around the core to assist in cutting and forming the core.
 8. The apparatus of claim 1 wherein said sleeve means includes at least two longitudinally disposed reinforcing means arranged at spaced positions at the periphery of said sleeve means to permit said sleeve means to collapse from at least said positions on its periphery.
 9. The apparatus of claim 1 wherein said sleeve has a preferentially collapsible portion near the bottom thereof.
 10. An apparatus for producing and retrieving subterranean formation cores which comprises: a tubular core barrel means; cutting means disposed at the lower portion of said core barrel means for cutting said core; collapsible sleeve means disposed within said core barrel means above said cutting means and defining a volume between the outer surface of said sleeve means and said core barrel, wherein fluid may be maintained under pressure; first valve means to maintain a fluid within said volume at a preselected pressure greater than the fluid pressure within said sleeve to maintain said sleeve in collapsed position until said core is received therein; and second valve means to exhaust fluid from said volume in response to decrease of said volume resulting from said core entering said sleeve.
 11. The apparatus of claim 10 wherein said tubular core barrel means comprises an outer barrel and an inner barrel defining a fluid channel therebetween, and wherein said first and second valve means communicate between said channel and said volume.
 12. The apparatus of claim 11 including means for exhausting fluid from said volume to said fluid channel means when said core enters said sleeve.
 13. The apparatus of claim 12 wherein said means for admitting fluid and said means for exhausting fluid comprise first and second one-way check valves which open at predetermined pressure gradients, and wherein the pressure gradient required to open said second valve is greater than that required to open said first valve.
 14. The apparatus of claim 11 wherein said outer barrel includes means for interconnection in a rotary well drilling string and wherein said outer barrel is rotatable independent of said inner barrel.
 15. The apparatus of claim 11 including fluid jet means in said cutting means communicating with said fluid channel means, said fluid jet means being disposed to direct fluid against the formation around the core to assist in the cutting and formation of said core.
 16. The apparatus of claim 11 wherein said means for admitting fluid is located at first position in said fluid channel means and including pressure equalizing means located at a second position in said fluid channel means downstream from said first position, said pressure equalizing means communicating between said fluid channel means and the interior of said sleeve to equalize fluid channel means and the interior of said sleeves to equalize fluid pressure therebetween.
 17. The apparatus of claim 10 including at least two longitudinal reinforcing means disposed around the periphery of said sleeve at regularly spaced positions and adapted to maintain the outer surface of said sleeve proximate to the inner surface of said inner barrel at said positions and permitting said sleeve means to collapse from said positions on its periphery in response to fluid pressure within said volume.
 18. Apparatus for producing and retrieving a formation core by rotary drilling which comprises: a core barrel structure comprising an outer barrel and an inner barrel defining a fluid channel therebetween, said outer barrel being freely rotatable relative to said inner barrel; a cutting means mounted on the lower portion of said outer barrel and rotatable with said outer barrel for cutting the formation to produce a core, said cutting means providing the termination of said fluid channel means; a tubular, collapsible sleeve disposed within said inner barrel above said cutting means for internally receiving the core produced, said sleeve means defining a volume between the outer surface thereof and said inner barrel; first check valve means fOr admitting fluid from a first position in said channel to said volume at a first pressure greater than the fluid pressure within said sleeve to collapse said sleeve prior to receipt of the core therein; second check valve means for exhausting fluid from said volume to said channel at a second pressure greater than said first pressure, said second pressure being insufficient to deform said core; and pressure equalization means disposed to equalize the fluid pressure between a second position in said channel downstream of said first position and the volume within said sleeve.
 19. Apparatus for producing and retrieving formation cores from beneath the surface of a body of water which comprises: a coring tube; cutting means on the lower end of said tube for producing said core; a collapsible sleeve disposed within said tube, said sleeve defining a sealable volume capable of retaining a fluid under pressure; differential pressure means to supply a fluid to said volume at a fluid pressure greater than hydrostatic pressure; exhaust check valve means disposed to exhaust fluid within said volume to said body of water, said check valve being openable in response to a preselected gradient between said pressure within said volume and hydrostatic pressure.
 20. A method for producing and retrieving a formation core which comprises: cutting the formation to produce a core; accepting said core axially into a collapsible sleeve; applying a fluid pressure to the outer surface of said sleeve to collapse said sleeve above said core; and controlling said fluid pressure behind said sleeve to permit yieldable expansion of said sleeve from the collapsed position to an expanded position to accept said core.
 21. The method of claim 20 wherein said core is cut by rotary drilling.
 22. The method of claim 20 including the step of circulating a fluid to the formation in the cutting region to assist in cutting said core.
 23. The method of claim 20 wherein said core is retrieved from a location under a hydrostatic head of pressure including the steps of raising said core while in said sleeve, and reducing said fluid pressure behind said sleeve in response to the reduction of hydrostatic pressure as said core is raised.
 24. A method for producing and retrieving a formation core from a borehole which comprises: cutting the formation to produce a core; establishing a fluid flow path to circulate a fluid to the bottom of said borehole in the cutting region, said fluid flow path offering resistance to said fluid flow to create a dynamic pressure drop across said path from a first position above the bottom of said borehole to a second lower position proximate the bottom of said borehole; accepting said core axially into a collapsible sleeve; applying a fluid pressure corresponding to said fluid pressure at said first position to the outer surface of said sleeve to collapse said sleeve above said core; equalizing dynamic fluid pressure between fluid at said second position and fluid within said sleeve; and controlling said pressure behind said sleeve to permit yieldable expansion of said sleeve to accept said core.
 25. The method of claim 24 wherein said core is cut by rotary drilling.
 26. The method of claim 24 including the steps of lifting said core from the bottom of said borehole; continuing circulation in said fluid path while said core is lifted from the bottom of said borehole; permitting the lower portion of said core to fall to the bottom of said borehole; and collapsing said sleeve below the remainder of said core to capture said core.
 27. The method of claim 24 wherein said borehole is filled with liquid including the additional steps of raising said core in said borehole; and reducing the pressure behind said sleeve in response to the reduction of hydrostatic pressure as said core is raised in said borehole. 